+static void predictValueUseListOrderImpl(const Value *V, const Function *F,
+ unsigned ID, const OrderMap &OM,
+ UseListOrderStack &Stack) {
+ // Predict use-list order for this one.
+ typedef std::pair<const Use *, unsigned> Entry;
+ SmallVector<Entry, 64> List;
+ for (const Use &U : V->uses())
+ // Check if this user will be serialized.
+ if (OM.lookup(U.getUser()).first)
+ List.push_back(std::make_pair(&U, List.size()));
+
+ if (List.size() < 2)
+ // We may have lost some users.
+ return;
+
+ bool IsGlobalValue = OM.isGlobalValue(ID);
+ std::sort(List.begin(), List.end(), [&](const Entry &L, const Entry &R) {
+ const Use *LU = L.first;
+ const Use *RU = R.first;
+ if (LU == RU)
+ return false;
+
+ auto LID = OM.lookup(LU->getUser()).first;
+ auto RID = OM.lookup(RU->getUser()).first;
+
+ // Global values are processed in reverse order.
+ //
+ // Moreover, initializers of GlobalValues are set *after* all the globals
+ // have been read (despite having earlier IDs). Rather than awkwardly
+ // modeling this behaviour here, orderModule() has assigned IDs to
+ // initializers of GlobalValues before GlobalValues themselves.
+ if (OM.isGlobalValue(LID) && OM.isGlobalValue(RID))
+ return LID < RID;
+
+ // If ID is 4, then expect: 7 6 5 1 2 3.
+ if (LID < RID) {
+ if (RID <= ID)
+ if (!IsGlobalValue) // GlobalValue uses don't get reversed.
+ return true;
+ return false;
+ }
+ if (RID < LID) {
+ if (LID <= ID)
+ if (!IsGlobalValue) // GlobalValue uses don't get reversed.
+ return false;
+ return true;
+ }
+
+ // LID and RID are equal, so we have different operands of the same user.
+ // Assume operands are added in order for all instructions.
+ if (LID <= ID)
+ if (!IsGlobalValue) // GlobalValue uses don't get reversed.
+ return LU->getOperandNo() < RU->getOperandNo();
+ return LU->getOperandNo() > RU->getOperandNo();
+ });
+
+ if (std::is_sorted(
+ List.begin(), List.end(),
+ [](const Entry &L, const Entry &R) { return L.second < R.second; }))
+ // Order is already correct.
+ return;
+
+ // Store the shuffle.
+ Stack.emplace_back(V, F, List.size());
+ assert(List.size() == Stack.back().Shuffle.size() && "Wrong size");
+ for (size_t I = 0, E = List.size(); I != E; ++I)
+ Stack.back().Shuffle[I] = List[I].second;
+}
+
+static void predictValueUseListOrder(const Value *V, const Function *F,
+ OrderMap &OM, UseListOrderStack &Stack) {
+ auto &IDPair = OM[V];
+ assert(IDPair.first && "Unmapped value");
+ if (IDPair.second)
+ // Already predicted.
+ return;
+
+ // Do the actual prediction.
+ IDPair.second = true;
+ if (!V->use_empty() && std::next(V->use_begin()) != V->use_end())
+ predictValueUseListOrderImpl(V, F, IDPair.first, OM, Stack);
+
+ // Recursive descent into constants.
+ if (const Constant *C = dyn_cast<Constant>(V))
+ if (C->getNumOperands()) // Visit GlobalValues.
+ for (const Value *Op : C->operands())
+ if (isa<Constant>(Op)) // Visit GlobalValues.
+ predictValueUseListOrder(Op, F, OM, Stack);
+}
+
+static UseListOrderStack predictUseListOrder(const Module &M) {
+ OrderMap OM = orderModule(M);
+
+ // Use-list orders need to be serialized after all the users have been added
+ // to a value, or else the shuffles will be incomplete. Store them per
+ // function in a stack.
+ //
+ // Aside from function order, the order of values doesn't matter much here.
+ UseListOrderStack Stack;
+
+ // We want to visit the functions backward now so we can list function-local
+ // constants in the last Function they're used in. Module-level constants
+ // have already been visited above.
+ for (auto I = M.rbegin(), E = M.rend(); I != E; ++I) {
+ const Function &F = *I;
+ if (F.isDeclaration())
+ continue;
+ for (const BasicBlock &BB : F)
+ predictValueUseListOrder(&BB, &F, OM, Stack);
+ for (const Argument &A : F.args())
+ predictValueUseListOrder(&A, &F, OM, Stack);
+ for (const BasicBlock &BB : F)
+ for (const Instruction &I : BB)
+ for (const Value *Op : I.operands())
+ if (isa<Constant>(*Op) || isa<InlineAsm>(*Op)) // Visit GlobalValues.
+ predictValueUseListOrder(Op, &F, OM, Stack);
+ for (const BasicBlock &BB : F)
+ for (const Instruction &I : BB)
+ predictValueUseListOrder(&I, &F, OM, Stack);
+ }
+
+ // Visit globals last, since the module-level use-list block will be seen
+ // before the function bodies are processed.
+ for (const GlobalVariable &G : M.globals())
+ predictValueUseListOrder(&G, nullptr, OM, Stack);
+ for (const Function &F : M)
+ predictValueUseListOrder(&F, nullptr, OM, Stack);
+ for (const GlobalAlias &A : M.aliases())
+ predictValueUseListOrder(&A, nullptr, OM, Stack);
+ for (const GlobalVariable &G : M.globals())
+ if (G.hasInitializer())
+ predictValueUseListOrder(G.getInitializer(), nullptr, OM, Stack);
+ for (const GlobalAlias &A : M.aliases())
+ predictValueUseListOrder(A.getAliasee(), nullptr, OM, Stack);
+ for (const Function &F : M) {
+ if (F.hasPrefixData())
+ predictValueUseListOrder(F.getPrefixData(), nullptr, OM, Stack);
+ if (F.hasPrologueData())
+ predictValueUseListOrder(F.getPrologueData(), nullptr, OM, Stack);
+ }
+
+ return Stack;
+}
+
+static bool isIntOrIntVectorValue(const std::pair<const Value*, unsigned> &V) {
+ return V.first->getType()->isIntOrIntVectorTy();
+}
+
+ValueEnumerator::ValueEnumerator(const Module &M)
+ : HasMDString(false), HasMDLocation(false), HasGenericDebugNode(false) {
+ if (shouldPreserveBitcodeUseListOrder())
+ UseListOrders = predictUseListOrder(M);